How Much Magnesium Per Day? Dosage by Age & Sex for Canada (2026)
Quick answer
For most adults, the supplemental dose is 200–350 mg of elemental magnesium a day, taken with food. That stays inside the 350 mg upper limit for magnesium from supplements, and tops up the 310–420 mg a day you need from food and pills together.
One catch nobody mentions: we read the Supplement Facts panel of 833 magnesium labels. The median serving is 250 mg — but follow the label's own directions and the median day comes to 399 mg, above the 350 mg limit.The numbers are below.
One option: Nutritionn Magnesium Glycinate 200mg Capsules, Pure Bisglycinate, 300 Count$0.33/day — 200 mg a capsule. The NIH supplemental limit is 350 mg a day.
Informational summary of NIH guidance and published clinical research — not medical advice. Talk to a clinician for personalised dosing, especially with kidney disease.
See the best magnesium picks →
How Much Magnesium Per Day?
Adult women need 310–320 mg of magnesium per day and adult men need 400–420 mg, from all sources combined (NIH RDA). The NIH upper limit for supplemental elemental magnesium is 350 mg a day. It applies to supplements only, not food. Follow the label serving and stay under that ceiling. Some trials used more under supervision; the table below shows the amounts studied.
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Find your magnesium dose
Answer a few questions for an estimate based on the NIH RDA. It's an estimate, not a prescription — talk to your clinician.
Recommended Daily Allowance (RDA)
These are the total daily magnesium needs from all sources (food + supplements), set by the National Institutes of Health:
| Age Group | Male | Female |
|---|---|---|
| 14-18 years | 410 mg | 360 mg |
| 19-30 years | 400 mg | 310 mg |
| 31+ years | 420 mg | 320 mg |
Source: NIH Office of Dietary Supplements
Want a smaller serving? Natural Factors Magnesium Bisglycinate 200 mg Powder, 120g$0.88/day is 200 mg and carries Health Canada NPN 80091128 (a licence, not independent lab testing).
Amounts Used in Published Trials
These are the elemental magnesium amounts reported in published trials. They are the amounts studied, not recommendations, and several are above the NIH supplemental limit.
| Topic | Amount Studied | Preferred Form | Timing | Evidence |
|---|---|---|---|---|
| Sleep quality | 320-500 mg/day | Ask your clinician | Varies by trial | Studied in older adults; results were small and mixed (Mah 2021 meta-analysis, PMID: 33865376) |
| General intake | 200-350 mg/day supplemental (NIH limit 350) | Glycinate or CitrateNutritionn Magnesium Glycinate 200mg Capsules, Pure Bisglycinate, 300 Count$0.33/day | With meals | NIH ODS (Zhao 2020 meta-analysis, PMID: 31758631) |
A well-absorbed glycinate: Nutritionn Magnesium Glycinate 200mg Capsules, Pure Bisglycinate, 300 Count$0.33/day. A citrate option: NOW Magnesium Citrate 200 mg (250 Tablets)$0.32/day.
Understanding Elemental vs Compound Weight
This is the most common source of dosing confusion. Supplement labels may list either the elemental magnesium or the total compound weight:
Gummies are where this bites hardest: a “600 mg” gummy label can carry 70 mg of elemental magnesium, and no magnesium gummy label we read reaches 300 mg a day.
| Item | Value (%) |
|---|---|
| Oxide | 60% |
| Citrate | 16% |
| Malate | 15% |
| Glycinate | 14% |
| Taurate | 9% |
| Threonate | 7.2% |
| Compound | % Elemental Mg | To get 400mg elemental Mg, you need: |
|---|---|---|
| Magnesium Oxide | 60% | ~670 mg of compound |
| Magnesium Citrate | 16% | ~2,500 mg of compound |
| Magnesium Glycinate | 14% | ~2,850 mg of compound |
| Magnesium L-Threonate | 7.2% | ~5,550 mg of compound |
| Magnesium Taurate | 9% | ~4,450 mg of compound |
| Magnesium Malate | 15% | ~2,670 mg of compound |
How to read the label: Look at the Supplement Facts panel for the line that says "Magnesium" followed by the form in parentheses (e.g., "Magnesium (as Magnesium Glycinate) ... 400 mg"). The number before "mg" is the elemental magnesium — that's the number that matters for dosing.
Prefer a powder? Here is an option: Natural Factors Magnesium Bisglycinate 200 mg Powder, 120g$0.88/day.
When to Take Magnesium
- Timing: Follow the label. Some people take glycinate in the evening.
- For general supplementation: Take with a meal. Food improves absorption and reduces the chance of digestive side effects.
- Citrate: Magnesium citrate has a laxative effect, stronger on an empty stomach. Our top citrate pick: NOW Magnesium Citrate 200 mg (250 Tablets)$0.32/day.
- Above the ceiling: Do not go above the everyday ceiling without your doctor's advice.
- Drug separation: If you take antibiotics (tetracyclines, quinolones) or bisphosphonates, take magnesium at least 2 hours before or 4-6 hours after.
Original research · Verified Supplement Data
What the label tells you to take
We read the Supplement Facts panel of 833 on-market magnesium labels in the NIH Dietary Supplement Label Database, and multiplied each serving by the maximum daily servings the label directs. That product — not the number on the front of the bottle — is the dose the label instructs.
The median serving on these labels is 250 mg; taken as directed, the median comes to 399 mg a day, above the 350 mg upper limit for supplemental magnesium.
- On the market
- 39,884
- Panels read
- 833
- Declaring a dose
- 825
- Stating a schedule
- 826
- Dose & schedule both
- 779
| Measure | 10th pct | Median | 90th pct |
|---|---|---|---|
| Per serving | 100 mg | 250 mg | 500 mg |
| As the label directs, per day | — | 399 mg | 500 mg |
| Servings per day | Labels | Share |
|---|---|---|
| 1 | 592 | 72% |
| 2 | 141 | 17% |
| 3 | 76 | 9% |
| 4 | 15 | 2% |
| 5 | 1 | <1% |
| 6 | 1 | <1% |
| Form | Labels | Median | 90th pct |
|---|---|---|---|
| Citrate | 376 | 250 mg | 500 mg |
| Oxide | 145 | 300 mg | 500 mg |
| Glycinate | 102 | 233 mg | 400 mg |
| Malate | 40 | 355 mg | 480 mg |
| Aspartate | 27 | 133 mg | 400 mg |
| Dose on the panel | Labels | Share |
|---|---|---|
| At or below the 420 mg RDA | 705 | 85% |
| Above the 420 mg RDA | 120 | 15% |
Both rows count the same 825 labels, so the shares add to 100%.
We only report figures that held up when we re-checked them. No figure is printed for: the share of labels at or above the upper limit.
Which form the market actually sells
- Magnesium Citrate44%
- Magnesium Oxide30%
- Magnesium Aspartate10%
- Magnesium Glycinate8%
- Magnesium Malate8%
Share of 805 chemical-form declarations across 833 labels — a single panel can name more than one.
What this means: The advice every guide ends on — follow the directions on the label — is where the problem starts. Per serving these products look compliant: a median of 250 mg against that ceiling. It is the directions that push them over, because a label that says "take two capsules twice daily" is prescribing four servings, and that multiplication happens nowhere on the front of the bottle. Read the Supplement Facts panel, then check how many servings a day it tells you to take, and multiply. The second number is your dose.
What to look for on the shelf
Two numbers on the panel, not one: the elemental magnesium per serving, and the servings a day it directs. Multiply them and keep the answer at or under 350 mg for everyday use. A 200 mg serving taken once clears that easily, which is why the picks on this page are dosed where they are — Natural Factors Magnesium Bisglycinate 200 mg Powder, 120g is 200 mg a serving and Health Canada NPN 80091128.
What this cannot tell you: This measures what labels declare and direct, not what is in the capsule and not what you absorb. It cannot tell you whether a product contains what it says — that needs assay testing, which DSLD does not do. Going over the supplemental limit commonly causes loose stools. It matters more if you have reduced kidney function, where magnesium clearance falls. Ask your clinician.
Source: NIH Dietary Supplement Label Database (DSLD) v9, read 2026-08-29. We only report findings that held up when we re-checked them.
Why the trials used more than the limit
You have now seen two numbers that look like they disagree. The NIH sets a Tolerable Upper Intake Level of 350 mg/day for supplemental magnesium, and the sleep trials in the table above ran at 320–500 mg. Both are correct, and the difference between them is the most useful thing on this page.
The NIH sets the ceiling based on diarrhea, the most common effect of too much supplemental magnesium in healthy adults. A trial running above the ceiling with a clinician watching is accepting that side effect on purpose.
Which means the ceiling is the number to use, and the trial dose is not, unless a clinician is supervising you. There is one important exception.
- Food is exempt. The limit covers supplements and magnesium-containing medications only. Dietary magnesium has no upper limit; your body regulates absorption from food.
- Kidney disease is the exception that matters. Magnesium clears through the kidneys, so reduced function turns an uncomfortable dose into a genuinely risky one. If your eGFR is below 60, the ceiling above does not apply to you — ask your doctor for a number.
- Real toxicity is rare and needs a much bigger dose. Hypermagnesemia — nausea, low blood pressure, facial flushing and muscle weakness, with serious effects at the highest levels — generally requires doses above 5,000 mg or existing renal failure.
- Split the dose if you go high. Two smaller doses with food are absorbed better and are gentler on the gut than one large one.
How Much Magnesium Are You Getting from Food?
Most people get 250-350mg/day from food — below the RDA for most adults. The best dietary sources:
- Pumpkin seeds (1 oz): 156 mg
- Spinach (1 cup cooked): 157 mg
- Dark chocolate (1 oz, 70-85%): 65 mg
- Almonds (1 oz): 80 mg
- Black beans (1/2 cup): 60 mg
- Avocado (1 medium): 58 mg
- Brown rice (1 cup cooked): 84 mg
Food comes first, and the 350 mg limit applies to supplements only. A healthcare provider can test serum magnesium levels, though this test only reflects ~1% of total body magnesium — some clinicians order an RBC magnesium test instead, though how well-validated that alternative actually is may surprise you.
Best magnesium to hit your dose
Most of the trials above used glycinate — well absorbed and gentle on the stomach. These three cover the 200–350 mg everyday range, ranked by cost per effective dose:
200 mg a serving. Well absorbed, gentle on the stomach.
Health Canada licensed (Health Canada NPN 80091128); sold as a powder.
Lowest cost per dose of the glycinates we carry.
Compare every pick on the magnesium glycinate page or the full best-magnesium ranking.
Frequently Asked Questions
How much magnesium should I take per day?
The RDA is 400-420mg/day for men and 310-320mg/day for women, and that figure covers food and supplements together. For a supplement on its own, follow the label serving; 350mg is the NIH upper limit for supplemental magnesium specifically. Some trials used more, under supervision.
When is the best time to take magnesium?
Magnesium is usually taken with food, which improves absorption and reduces stomach upset. See our full best time to take magnesium guide.
Can you take too much magnesium?
The supplemental upper limit is 350mg/day (NIH). Exceeding this commonly causes diarrhea. Serious toxicity is rare but can occur with very high doses or kidney disease. Magnesium glycinate is usually reported as the form least likely to cause GI side effects, though no trial has compared forms at the same elemental dose.
What's the difference between elemental magnesium and compound weight?
Magnesium supplements are magnesium bonded to another molecule. "Elemental magnesium" is the actual Mg content your body uses. A 2,000mg magnesium glycinate capsule may contain only ~280mg elemental Mg. Always check the Supplement Facts label for the elemental amount.
How much magnesium should older adults (seniors) take?
The RDA doesn't rise with age — it stays 420mg/day for men and 320mg/day for women over 30.
How much magnesium should a woman take per day?
The RDA for adult women is 310mg/day (ages 19-30) or 320mg/day (31+).
Should I take a magnesium supplement while pregnant?
Ask your prenatal provider before taking any supplement, including magnesium.
Bottom line: our value pick is Nutritionn Magnesium Glycinate 200mg Capsules, Pure Bisglycinate, 300 Count$0.33/day. For a citrate option, see NOW Magnesium Citrate 200 mg (250 Tablets)$0.32/day.
Related Guides
- Magnesium side effects and too much magnesium — diarrhea by form, the 350 mg supplemental UL, and who must be careful
- Magnesium Glycinate: Products & Cost per Dose — Every verified pick, ranked
- Magnesium Forms Compared — Forms, absorption, and elemental magnesium
- Best Magnesium for Sleep — Products ranked by cost per effective dose
- Signs of Magnesium Deficiency — How to know if you need it
- Glycinate vs Citrate — The most common form comparison question
- How Much Magnesium for Seniors? — Same RDA; talk to your clinician about kidney function after 65
- How Much Magnesium for Women? — Full RDA table by age
- How Long Does Magnesium Take to Work? — What the trials actually timed, by goal
- RBC Magnesium Test — What the evidence for the "better" test actually shows
- Vitamin D Dosage Guide — If supplementing both; magnesium is needed for vitamin D conversion
- All Magnesium Guides
Sources
- NIH Office of Dietary Supplements. "Magnesium: Fact Sheet for Health Professionals." ods.od.nih.gov
- Mah J, Pitre T. "Oral magnesium supplementation for insomnia in older adults." BMC Complement Med Ther. 2021;21(1):125. PMID: 33865376
- Firoz M, Graber M. "Bioavailability of US commercial magnesium preparations." Magnes Res. 2001;14(4):257-62. PMID: 11794633
- U.S. Department of Agriculture FoodData Central. fdc.nal.usda.gov
- Boyle NB, et al. “The Effects of Magnesium Supplementation on Subjective Anxiety and Stress-A Systematic Review.” Nutrients. 2017. PMID: 28445426
- McCabe D, et al. “The impact of essential fatty acid, B vitamins, vitamin C, magnesium and zinc supplementation on stress levels in women: a systematic review.” JBI database of systematic reviews and implementation reports. 2017. PMID: 28178022
- Argeros Z, et al. “Magnesium Supplementation and Blood Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.” Hypertension (Dallas, Tex. : 1979). 2025. PMID: 41000008
- Zhang X, et al. “Effects of Magnesium Supplementation on Blood Pressure: A Meta-Analysis of Randomized Double-Blind Placebo-Controlled Trials.” Hypertension (Dallas, Tex. : 1979). 2016. PMID: 27402922
- Noah L, et al. “Effect of magnesium and vitamin B6 supplementation on mental health and quality of life in stressed healthy adults: Post-hoc analysis of a randomised controlled trial.” Stress and health : journal of the International Society for the Investigation of Stress. 2021. PMID: 33864354
- Garrison SR, et al. “Magnesium for skeletal muscle cramps.” The Cochrane database of systematic reviews. 2020. PMID: 32956536
- Morishita D, et al. “Senna Versus Magnesium Oxide for the Treatment of Chronic Constipation: A Randomized, Placebo-Controlled Trial.” The American journal of gastroenterology. 2021. PMID: 32969946
- van der Schoot A, et al. “The effect of food, vitamin, or mineral supplements on chronic constipation in adults: A systematic review and meta-analysis of randomized controlled trials.” Neurogastroenterology and motility. 2023. PMID: 37243443
- Tarsitano MG, et al. “Effects of magnesium supplementation on muscle soreness in different type of physical activities: a systematic review.” Journal of translational medicine. 2024. PMID: 38970118
- Heffernan SM, et al. “The Role of Mineral and Trace Element Supplementation in Exercise and Athletic Performance: A Systematic Review.” Nutrients. 2019. PMID: 30909645